Performance of two Picea abies (L.) Karst. stands at different stages of decline

Summary This is the first in a series of papers on the growth, photosynthetic rate, water and nutrient relations, root distribution and mycorrhizal frequency of two Norway spruce forests at different stages of decline. One of the stands was composed of green trees only while the other included trees ranging in appearance from full green crowns to thin crowns with yellow needles. In this paper we compare the growth and carbohydrate relations of the two stands and examine relationships among growth variables in ten plots. The declining stand produced 65 percent of the wood per ground area compared with the stand in which all trees were green because its foliage produced less wood at any level of leaf area index. The difference in foliage efficiency between the sites could not be explained by differeneces in climate, competition or stand structure. The declining stand appeared to have lower carbon gain as indicated by a smaller increase in reserve carbohydrates before bud break, and weaker sinks for carbohydrates as indicated by less use of the stored carbohydrates than the healthy stand. Thus, growth reduction was probably related to factors which affect both photosynthesis and, even more, the sinks for carbohydrate.     

Investigations on phosphate uptake and polyphosphate metabolism by mycorrhized and nonmycorrhized roots of beech and pine as investigated by in vivo 31P-NMR

Comparative in vivo ³¹P-NMR studies of mycorrhized and nonmycorrhized roots of Fagus sylvatica and Pinus sylvestris and of the fungus Suillus bovinus in pure culture have produced interesting new data. With respect to intracellular compartments and pH, ³¹P-NMR spectroscopy showed that the spectrum of the mycorrhiza results from simple superimposition of the spectra of its symbionts. A special method of cyclic phosphate supply followed by block averaging of the NMR spectra was used to determine the kinetic behaviour of phosphate uptake and storage and its incorporation into polyphosphate at a constant external pH of 5.5. Mycorrhized roots and pure fungus showed transformation of accumulated inorganic phosphate into mobile polyphosphate with a medium chain length. Transformation of mobile into immobile polyphosphate either with a long chain length or in a granular state was also observed. Thus, two different types of fungal polyphosphate could be verified. Deficiency of external phosphate initiated the mobilization of internal phosphate, transforming stored polyphosphate into phosphate. It could be shown that a high fungal mass renders mycorrhizal phosphate metabolism less sensitive to external variation in nutrient concentration. The central role of the fungus in regulating mycorrhizal phosphate metabolism is discussed.